Light-emitting device and iridium complex

ABSTRACT

A light-emitting device comprising a pair of electrodes, and organic compound layers comprising a light-emitting layer provided in between the electrodes, wherein at least one of the organic compound layers comprises a compound having a transition metal atom-phosphorus atom bond.

CROSS REFERENCE

This is a Divisional Application of prior application Ser. No.09/956,007 filed Sep. 20, 2001, the disclosure of which is incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to a material for a light-emitting device whichcan convert electric energy to light, and to a light-emitting devicewhich can suitably be utilized in the field of display device, display,back light, electrophotography, light source for illumination, lightsource for recording, light source for exposure, light source forreadout, mark, billboard, interior decoration, optical communication andthe like. In addition, it relates to an iridium complex showing a strongemission in a blue region.

BACKGROUND OF THE INVENTION

At the present time, development and study on various display devicesare aggressively driven. In particular, organic electric fieldlight-emitting (EL) can obtain highly bright luminescence at a lowvoltage and accordingly, is drawing an attention as a promising displaydevice. For example, a light-emitting device comprising an organic thinfilm formed by depositing an organic compound is known (Applied Physics25 Letters, Vol. 51, page 913 (1987)). The light-emitting devicedescribed in this publication has a laminate structure wherein atris(8-hydroxyquinolinato) aluminum complex (Alq) is used as an electrontransporting material and is layered on a hole transporting material (anamine compound), and is greatly improved in the luminescence propertiesdue to the structure as compared with conventional single-layer devices.

In recent years, it has actively been investigated to apply organic ELdevices to color display or white light source. However, in order todevelop high performance color display and white light source, it isnecessary to improve properties of each of blue light-emitting devices,green light-emitting devices and red light-emitting devices.

As a means for improving the properties of light-emitting devices, agreen light-emitting device utilizing luminescence emitted from anortho-metalated iridium complex (Ir(ppy)₃: Tris-Ortho-Metalated Complexof Iridium(III) with 2-Phenylpyridine) has been reported (AppliedPhysics Letters 75, 4 (1999)). However, since Ir(ppy)₃ emits only greenlight, it can be applied to only a limited scope of display. Thus,development of devices capable of emitting other color light (blue orred light) with a high efficiency have been required.

SUMMARY OF THE INVENTION

The present invention provides a light-emitting device with a highefficiency, and provides a novel metal complex capable of actualizingthe device.

The above-described subjects of the invention can be solved by thefollowing:

(1) A light-emitting device comprising:

-   -   a pair of electrodes; and    -   organic compound layers comprising a light-emitting layer        provided in between the electrodes,    -   wherein at least one of the organic compound layers comprises a        compound having a transition metal atom-phosphorus atom bond.

(2) The light-emitting device set forth in (1) above, wherein thecompound having a transition metal atom-phosphorus atom bond isrepresented by the following formula (2):

wherein R²¹ represents a hydrogen atom or a substituent, L²¹ representsa ligand, X²¹ represents a counter ion, n²¹ represents 2 or 3, n²²represents an integer of 1 to 8, n²³ represents an integer of 0 to 8,n²⁴ represents an integer of 0 to 6, and, when n²¹, n²², n²³ or n²⁴represents a plural number, R²¹ groups, (R²¹)_(n21)—P ligands, L²¹ligands or X²¹ ions are each the same or different.

(3) The light-emitting device set forth in (1) above, wherein thecompound having a transition metal atom-phosphorus atom bond is acompound having a maximum emitted wavelength, λmax, in a range of 350 nmto 550 nm.

(4) The light-emitting device set forth in (1) above, wherein the layercomprising the compound having a transition metal atom-phosphorus atombond is a layer formed by a coating process.

(5) The light-emitting device set forth in (1) above, wherein thecompound having a transition metal atom-phosphorus atom bond isrepresented by the following formula (4):

wherein R⁴¹, R⁴², R⁴³, R⁴⁴ and R⁴⁵ each independently represent asubstituent, L⁴¹ represents a ligand, X⁴¹ represents a counter anion,m⁴¹ and m⁴² each independently represent an integer of 0 to 4, and n⁴¹represents 0 or 1.

(6) The light-emitting device set forth in (1) above, wherein thecompound having a transition metal atom-phosphorus atom bond isrepresented by the following formula (5):

wherein R⁵¹, R⁵², R⁵³, R⁵⁴, R⁵⁵ and R⁵⁶ each independently represent asubstituent, Z⁵¹ represents a linkage group, X⁵¹ represents a counteranion, and m⁵¹ and m⁵² each independently represent an integer of 0 to4.

(7) The light-emitting device set forth in (1) above, wherein thecompound having a transition metal atom-phosphorus atom bond isrepresented by the following formula (6):

wherein R⁶¹, R⁶², R⁶³, R⁶⁴ and R⁶⁵ each independently represent asubstituent, Z⁶¹ represents a linkage group, and m⁶¹ and m⁶² eachindependently represent an integer of 0 to 4.

(8) The light-emitting device set forth in (5) above, wherein L⁴¹represents a halogen atom or a cyano group.

(9) The light-emitting device set forth in (6) above, wherein Z⁵¹represents an alkylene group or an arylene group.

(10) The light-emitting device set forth in (7) above, wherein Z⁶¹represents an alkylene group or an arylene group.

(11) The light-emitting device set forth in (5) above, wherein thecompound represented by the formula (4) has a maximum emittedwavelength, λmax, in a range of 350 nm to 550 nm.

(12) The light-emitting device set forth in (6) above, wherein thecompound represented by the formula (5) has a maximum emittedwavelength, λmax, in a range of 350 nm to 550 nm.

(13) The light-emitting device set forth in (7) above, wherein thecompound represented by the formula (6) has a maximum emittedwavelength, λmax, in a range of 350 nm to 550 nm.

(14) The light-emitting device set forth in (5) above, wherein the layercomprising the compound represented by the formula (4) is a layer formedby a coating process.

(15) The light-emitting device set forth in (6) above, wherein the layercomprising the compound represented by the formula (5) is a layer formedby a coating process.

(16) The light-emitting device set forth in (7) above, wherein the layercomprising the compound represented by the formula (6) is a layer formedby a coating process.

(17) A compound represented by the following formula (4):

wherein R⁴¹, R⁴², R⁴³, R⁴⁴ and R⁴⁵ each independently represent asubstituent, L⁴¹ represents a ligand, X⁴¹ represents a counter anion,m⁴¹ and m⁴² each independently represent an integer of 0 to 4, and n⁴¹represents 0 or 1.

(18) A compound represented by the following formula (5):

wherein R⁵¹, R⁵², R⁵³, R⁵⁴, R⁵⁵ and R⁵⁶ each independently represent asubstituent, Z⁵¹ represents a linkage group, X⁵¹ represents a counteranion, and m⁵¹ and m⁵² each independently represent an integer of 0 to4.

(19) A compound represented by the following formula (6):

wherein R⁶¹, R⁶², R⁶³, R⁶⁴ and R⁶⁵ each independently represent asubstituent, Z⁶¹ represents a linkage group, and m⁶¹ and m⁶² eachindependently represent an integer of 0 to 4.

(20) The light-emitting device set forth in (1) above, wherein thetransition metal atom is an atom selected from the group consistingruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium andplatinum.

(21) The light-emitting device set forth in (1) above, wherein thephosphorus atom constitutes a part of phosphorus ligand.

(22) The light-emitting device set forth in (21) above, wherein thephosphorus ligand is selected from the group consisting of analkylphosphine and derivatives thereof, an arylphosphine and derivativesthereof, heteroarylphosphine and derivatives thereof, an alkoxyphosphineand derivatives thereof, an aryloxyphosphine and derivatives thereof, aheteroaryloxyaminophosphine and derivatives thereof, a phosphinine(phosphabenzene) and derivatives thereof, and aminophosphine andderivatives thereof.

(23) The light-emitting device set forth in (1) above, wherein x valueon the CIE chromaticity diagram of the emitting is 0.22 or less, and yvalue on the CIE chromaticity diagram of the emitting is 0.53 or less.

(24) The light-emitting device set forth in (1) above, which emitsspectrum having a half band width of 1 nm to 100 nm.

(25) The light-emitting device set forth in (2) above, wherein thevalence number of iridium is trivalent.

(26) The light-emitting device set forth in (1) above, wherein thecontent of the compound having a transition metal atom-phosphorus atombond in the light-emitting layer is from 0.1% to 100% by weight based onthe total composition of the light-emitting layer.

(27) The light-emitting device set forth in (1) above, wherein thecontent of the compound having a transition metal atom-phosphorus atombond in the light-emitting layer is from 1% to 50% by weight based onthe total composition of the light-emitting layer.

(28) The light-emitting device set forth in (1) above, wherein thecontent of the compound having a transition metal atom-phosphorus atombond in the light-emitting layer is from 5% to 30% by weight based onthe total composition of the light-emitting layer.

DETAILED DESCRIPTION OF THE INVENTION

The invention is described below in detail.

A light-emitting device according to the invention contains a compoundhaving at least one bond formed between transition metal atom andphosphorus atom (hereinafter abbreviated as “present compound”). Thepresent compound is not particularly limited in its transition metalatom, but it is preferable that the transition metal atom be ruthenium,rhodium, palladium, tungsten, rhenium, osmium, iridium or platinum, morepreferably rhenium, iridium or platinum.

The phosphorus atom binding to one of these transition metal atompreferably constitutes a part of phosphorus ligand.

As to the phosphorus ligand, the invention has no particular limitation,but a wide variety of known phosphorus ligands and derivatives thereofcan be used (with examples including the ligands described, e.g., in G.Wilkinson, Comprehensive Coordination Chemistry, Pergamon Press Co.(1987), H. Yersin, Photochemistry and Photophysics of CoordinationCompounds, Springer-Verlag A. G. (1987), and Akio Yamamoto, Yuki KinzokuKagagu-Kiso to Oyo—(which may be translated “OrganometallicChemistry—Fundamentals and Applications—”), Shokabo Co. (1982). Suitableexamples of a phosphorus ligand contained in the present compoundinclude an alkylphosphine and derivatives thereof, an arylphosphine andderivatives thereof, heteroarylphosphine and derivatives thereof, analkoxyphosphine and derivatives thereof, an aryloxyphosphine andderivatives thereof, a heteroaryloxyaminophosphine and derivativesthereof, a phosphinine (phosphabenzene) and derivatives thereof, andaminophosphine and derivatives thereof.

Besides a phosphorus ligand as recited above, the present compound canhave various known ligands (e.g., the ligands as described in G.Wilkinson, Comprehensive Coordination Chemistry, Pergamon Press Co.(1987), H. Yersin, Photochemistry and Photophysics of CoordinationCompounds, Springer-Verlag A. G. (1987), and Akio Yamamoto, Yuki KinzokuKagaku-Kiso to Oyo—(which means “Organometallic Chemistry—Fundamentalsand Applications—”), Shokabo Co. (1982)). Suitable examples of suchligands include halogen ligands (preferably chlorine ligand),nitrogen-containing heterocycle ligands (e.g., phenylpyridine,benzoquinoline, quinolinole, bipyridyl, phenanthroline), diketoneligands (e.g., acetylacetone), carboxylate ligands (e.g., acetic acidligand), a carbon monoxide ligand, an isonitrile ligand and a cyanoligand. Of these ligands, nitrogen-containing heterocycle ligands arepreferred over the others.

The present compound may contain one transition metal atom, or it may bethe so-called polynuclear complex wherein two or more transition metalatoms are present. Further, the present compound may contain other metalatoms in addition to transition metal atom.

It is appropriate that the present compound have a maximum emittedwavelength ranging from 350 nm to 550 nm, preferably from 380 nm to 500nm, particularly preferably from 400 nm to 480 nm.

From the viewpoint of blue color purity of luminescence color, it ismore advantageous that the smaller x and y values the light-emittingdevice containing the present compound has on the CIE chromaticitydiagram. More specifically, the suitable x value on the CIE chromaticitydiagram of the luminescence is at most 0.22, preferably at most 0.20;while the suitable y value on the CIE chromaticity diagram of theluminescence is at most 0.53, preferably at most 0.50, particularlypreferably at most 0.40.

From the viewpoint of blue color purity, it is also favorable that theluminescence spectrum of the light-emitting device containing thepresent compound has a half width of 1 to 100 nm, preferably 5 to 90 nm,more preferably 10 to 80 nm, particularly preferably 20 to 70 nm.

The present compound is preferably embodied in compounds represented byformula (1).

The compounds represented by formula (1) are illustrated below.

R¹ represents a hydrogen atom or a substituent, M¹ represents atransition metal ion, L¹ represents a ligand, and X¹ represents acounter ion. n¹ represents 2 or 3, n² represents an integer of 1 to 8,n³ represents an integer of 0 to 8, and n⁴ represents an integer of 0 to6. When at least one of n¹, n², n³ and n⁴ is more than one,corresponding two or more R¹ groups, two or more (R¹)_(n1)—P ligands,two or more L¹ ligands and two or more X¹ ions may be each individuallythe same or different. (R¹)_(n1)—P ligands, L¹ ligands, or (R¹)_(n1)—Pand L¹ ligands may combine with each other and form a chelate ligand.

Suitable examples of a substituent represented by R¹ include an alkylgroup containing preferably 1 to 30 carbon atoms, more preferably 1 to20 carbon atoms, particularly preferably 1 to 10 carbon atoms (e.g.,methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl,cyclopropyl, cyclopentyl, cyclohexyl), an alkenyl group containingpreferably 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms,particularly preferably 2 to 10 carbon atoms (e.g., vinyl, allyl,2-butenyl, 3-pentenyl), an alkynyl group containing preferably 2 to 30carbon atoms, more preferably from 2 to 20 carbon atoms, particularlypreferably 2 to 10 carbon atoms (e.g., propargyl, 3-pentynyl), an arylgroup containing preferably 6 to 30 carbon atoms, more preferably 6 to20 carbon atoms, particularly 6 to 12 carbon atoms (e.g., phenyl,p-methylphenyl, naphthyl, anthranyl), an amino group containingpreferably 0 to 30 carbon atoms, more preferably 0 to 20 carbon atoms,particularly preferably 0 to 10 carbon atoms (e.g., amino, methylamino,dimethylamino, diethylamino, dibenzylamino, diphenylamine,ditolylamino), an alkoxy group containing preferably 1 to 30 carbonatoms, more preferably 1 to 20 carbon atoms, particularly preferably 1to 10 carbon atoms (e.g., methoxy, ethoxy, butoxy, 2-ethylhexyloxy), anaryloxy group containing preferably 6 to 30 carbon atoms, morepreferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbonatoms (e.g., phenyloxy, 1-naphthyloxy, 2-naphthyloxy), a heteroaryloxygroup containing preferably 1 to 30 carbon atoms, more preferably 1 to20 carbon atoms, particularly preferably 1 to 12 carbon atoms (e.g.,pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy), an acyl groupcontaining preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, particularly preferably 1 to 12 carbon atoms (e.g.,acetyl, benzoyl, formyl, pivaroyl), an alkoxycarbonyl group containingpreferably 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms,particularly preferably 2 to 12 carbon atoms (e.g., methoxycarbonyl,ethoxycarbonyl), an aryloxycarbonyl group containing preferably 7 to 30carbon atoms, more preferably 7 to 20 carbon atoms, particularlypreferably 7 to 12 carbon atoms (e.g., phenyloxycarbonyl), an acyloxygroup containing preferably 2 to 30 carbon atoms, more preferably 2 to20 carbon atoms, particularly preferably 2 to 10 carbon atoms (e.g.,acetoxy, benzoyloxy), an acylamino group containing preferably 2 to 30carbon atoms, more preferably 2 to 20 carbon atoms, particularlypreferably 2 to 10 carbon atoms (e.g., acetylamino, benzoylamino), analkoxycarbonylamino group containing preferably 2 to 30 carbon atoms,more preferably 2 to 20 carbon atoms, particularly preferably 2 to 12carbon atoms (e.g., methoxycarbonylamino), an aryloxy carbonylaminogroup containing preferably 7 to 30 carbon atoms, more preferably 7 to20 carbon atoms, particularly preferably 7 to 12 carbon atoms (e.g.,phenyloxycarbonylamino), a sulfonylamino group containing preferably 1to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularlypreferably 1 to 12 carbon atoms (e.g., methanesulfonylamino,benzenesulfonylamino), a sulfamoyl group containing preferably 0 to 30carbon atoms, more preferably 0 to 20 carbon atoms, particularlypreferably 0 to 12 carbon atoms (e.g., sulfamoyl, methylsulfamoyl,dimethylsulfamoyl, phenylsulfamoyl), a carbamoyl group containingpreferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms,particularly preferably 1 to 12 carbon atoms (e.g., carbamoyl,methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl), an alkylthio groupcontaining preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, particularly preferably 1 to 12 carbon atoms (e.g.,methylthio, ethylthio), an arylthio group containing preferably 6 to 30carbon atoms, more preferably 6 to 20 carbon atoms, particularlypreferably 6 to 12 carbon atoms (e.g., phenylthio), a heteroarylthiogroup containing preferably 1 to 30 carbon atoms, more preferably 1 to20 carbon atoms, particularly preferably 1 to 12 carbon atoms (e.g.,pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio,2-benzothiazolylthio), a sulfonyl group containing preferably 1 to 30carbon atoms, more preferably 1 to 20 carbon atoms, particularlypreferably 1 to 12 carbon atoms (e.g., mesyl, tosyl), a sulfinyl groupcontaining preferably 1 to 30 carbon atoms, more preferably 1 to 20carbon atoms, particularly preferably 1 to 12 carbon atoms (e.g.,methanesulfinyl or benzenesulfinyl), an ureido group containingpreferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms,particularly preferably 1 to 12 carbon atoms (e.g., ureido,methylureido, phenylureido), a phosphoric acid amido group containingpreferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms,particularly preferably 1 to 12 carbon atoms (e.g., diethylphosphoricacid amido, phenylphosphoric acid amido), a hydroxyl group, a mercaptogroup, a halogen atom (e.g., fluorine, chlorine, bromine, iodine), acyano group, a sulfo group, a carboxyl group, a nitro group, ahydroxamic acid group, a sulfino group, a hydrazino group, an iminogroup, a heterocyclic group (including aliphatic heterocyclic groups andheteroaryl groups, and containing preferably 1 to 30, more preferably 1to 12 carbon atoms, and hetero atom or atoms such as nitrogen atom,oxygen atom or sulfur atom, specific examples including imidazolyl,pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl,benzimidazolyl, benzothiazolyl and carbamoyl), a silyl group containingpreferably 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms,particularly preferably 3 to 24 carbon atoms (e.g., trimethylsilyl,triphenylsilyl), and a phosphino group containing preferably 2 to 30carbon atoms, more preferably 2 to 12 carbon atoms (e.g.,dimethylphosphino, diphenylphosphino). Each of these substituents mayfurther be substituted.

A plurality of R¹ groups may combine with each other to form a cyclicstructure. And atoms on R¹ groups may combine with M¹ to form theso-called chelate complex, or R¹ and L¹ may combine together to form achelate ligand.

Of the groups recited above, alkyl, aryl, heteroaryl, alkoxy, aryloxy,heteroaryloxy and substituted amino groups, and groups formingphosphinine rings (phosphabenzene rings) are preferred as R¹ groups overthe others. It is advantageous that at least one of R¹ groups is analkoxy, aryloxy or heteroaryloxy group, especially an alkoxy or aryloxygroup.

Further, it is appropriate that the phosphorus ligands contained in thepresent compound be chelate ligands.

M¹ represents a transition metal atom. Suitable examples of such atransition metal include ruthenium, rhodium, palladium, tungsten,rhenium, osmium, iridium and platinum. Of these metals, rhenium, iridiumand platinum are preferred over the others.

L¹ represents a ligand. Such a ligand includes the ligands describedabove as ligands which the present compound can contain in addition tophosphorus ligands. As suitable examples thereof, mention may be made ofhalogeno ligands (preferably chlorine ligand), nitrogen-containingheterocycle ligands (such as phenylpyridine, benzoquinoline, quinolinol,bipyridyl and phenanthroline), diketone ligands (e.g., acetylacetone)),carboxylic acid ligands (e.g., acetic acid ligands), a carbon monoxideligand, an isonitrile ligand, and a cyano ligand. Of these ligands,nitrogen-containing heterocycle ligands are preferred over the others.

X¹ represents a counter ion. There is no particular limitation on such acounter ion, but it is appropriate for the counter ion to be an alkalimetal ion, an alkaline earth metal ion, a halogen ion, perchlorate ion,PF₆ion, or an ammonium ion (e.g., tetramethylammonium ion).

n¹ is preferably 3. n² is preferably 1, 2 or 3. n³ is preferably 0, 1, 2or 3. n⁴ is preferably 0, 1, 2 or 3.

As the present compound, compounds represented by formula (2) or formula(7) (especially compounds represented by formula (2)) are advantageousover the others. As the compounds represented by formula (2), compoundsrepresented by formula (8) are desirable, and compounds represented byformula (3) are more desirable.

As the compounds represented by formula (3), compounds represented byformulae (4), (5) and (6) respectively are preferable. In particular,the compounds represented by formula (5) are advantageous.

Explanations of the formula (2) are made below. R²¹, L²¹, X²¹, n²¹, n²²,n²³ and n²⁴ have the same meanings as R¹, L¹, X¹, n₁ , n², n³ and n⁴respectively, and each pair are also identical in preferred range.

The compounds represented by formula (2) are not particularly limited asto the valence number of iridium, but it is preferable for the iridiumcontained therein to be trivalent. Each of those compounds may containone iridium atom, or may be the so-called polynuclear complex containingtwo or more iridium atoms (for instance, which may contain an iridiumatom in L²¹ or R²¹). However, compounds containing one iridium atom permolecule are preferred. Although another metal atom may be containedtherein in addition to the iridium atom, it is appropriate for thecompound to contain an iridium atom alone.

The formula (3) is explained below. R³¹, X³¹ and n³¹ have the samemeanings as R¹, X¹ and n¹ respectively, and each pair are also identicalin preferred range. A plurality of R³¹ groups may be the same ordifferent. R³² and R³³ each represent a substituent, with examplesincluding the groups recited above as those represented by R¹.Specifically, the groups suitable for R³² are an alkyl group, an arylgroup and a halogen atom. Of these groups, an alkyl group and a fluorineatom are preferred over the others. The groups suitable as R³³ are analkyl group, an aryl group, an amino group and an alkoxy group. Of thesegroups, an alkyl group and an alkoxy groups are preferred over theothers. Atoms contained in R³² and R³³ may be bonded to the iridiumatom.

m³¹ and m³² represents an integer of 0 to 4, preferably 0 to 2. When m³¹and m³² each represent an integer more than one, R³² groups may be thesame or different and R³³ groups also may be the same or different. n³⁴represents 0 or 1.

L³¹ represents a monodentate ligand, or a ligand forming a chelatestructure by binding with R³¹. The ligands suitable as L³¹ are ahalogeno ligand, a ligand forming a chelate structure by binding withR³¹, and a cyano ligand. Of these ligands, the ligand forming a chelatestructure by binding with R³¹ is preferred over the others.

n³⁴ represents 0 or 1. When L³¹ is an anionic ligand, n³⁴ is 0; while,when L³¹ is a nonionic ligand, n³⁴ is 1.

The formula (4) is explained below. R⁴¹, R⁴², R⁴³, R⁴⁴ and R⁴⁵ eachrepresent a substituent. As the substituent represented by R⁴¹, an alkylgroup, an aryl group or a heteroaryl group is suitable. Examples andpreferred ranges of substituents represented by R⁴⁴ and R⁴⁵ are the sameas those of R¹. Examples and preferred ranges of substituentsrepresented by R⁴² and R⁴³ are the same as those of R³² and R³³respectively.

L⁴¹ represents a monodentate ligand, or a ligand forming a chelatestructure by binding with R⁴¹ or R⁴⁵. The ligands preferred as L⁴¹ are ahalogen ligand, a ligand forming a chelate structure by binding with R⁴¹or R⁴⁵ and a cyano ligand.

m⁴¹ and m⁴² have the same meanings as m³¹ and m³² respectively, andpreferred ranges thereof are the same as those of m³¹ and m³²respectively.

n⁴¹ represents 0 or 1. When L⁴¹ is an anionic ligand, n⁴¹ is 0; while,when L⁴¹ is a nonionic ligand, n⁴¹ is 1.

The formula (5) is explained below. R⁵¹, R⁵², R⁵³, R⁵⁴R⁵⁵ and R⁵⁶ eachrepresent a substituent. Examples and preferred ranges of R⁵¹ and R⁵²are the same as those of R³² and R³³ respectively. It is appropriate forR⁵³, R⁵⁴, R⁵⁵ and R⁵⁶ each to be an alkyl group, an aryl group or analkoxy group.

Z⁵¹ represents a linkage group. Examples of such a linkage group includean alkylene group (such as methylene, ethylene, trimethylene, propyleneor tetramethylene), an alkenylene group (such as vinylene), an arylenegroup (such as o-phenylene, 2,3-pyridyiene), an oxygen linkage, a sulfurlinkage, a carbonyl linkage, a sulfonyl linkage, a sulfoxide linkage,and a linkage group having two or more of the linkage groups recitedabove (such as ethyleneoxy, 2,2-binaphthyl and —O(C═O)O—). These linkagegroups may further have substituents. As examples of such substituents,mention may be made of the groups recited in the explanations of R¹. Ofthe linkage groups recited above as Z⁵¹, an alkylene group, an arylenegroup, an oxygen linkage and a linkage group having two or more of theselinkage groups are preferred over the others. In particular, it isadvantageous that Z⁵¹ is an o-phenylene group.

X⁵¹ represents a counter anion. Examples and a preferred range of X⁵¹are the same as those of X⁴¹. m⁵¹ and m⁵² each represent an integer of 0to 4, and the preferred ranges thereof are the same as those of m³¹ andm³² respectively.

The formula (6) is explained below. R⁶¹, R⁶², R⁶³, R⁶⁴ and R⁶⁵ eachrepresent a substituent. Examples and preferred ranges of R⁶¹ and R⁶²are the same as those of R³² and R³³ respectively. It is appropriate forR⁶³ and R⁶⁴ each to be an alkyl group, an aryl group or an alkoxy group,and for R⁶⁵ to be an aryl group, a heteroaryl group, an acyl group, asulfonyl group or a phosphonyl group. Z⁶¹ represents a linkage group,and the preferred range thereof is the same as that of Z⁵¹. m⁶¹ and m⁶²each represent an integer of 0 to 4, and the preferred ranges thereofare the same as those of m³¹ and m³² respectively.

The formula (7) is explained below. R⁷¹, L⁷¹, X⁷¹ and n⁷¹ have the samemeanings as R¹, L¹, X¹ and n¹ respectively, and preferred ranges thereofare the same as those of R¹, L¹, X¹ and n¹ respectively. n⁷² representsan integer of 1 to 4, preferably 1 or 2. n⁷³ represents an integer of 0to 4, preferably 0 or 1. n⁷⁴ represents an integer of 0 to 2, preferably0 or 1.

The formula (8) is explained below. R⁸¹, R⁸² and R⁸³ each have the samemeaning as R¹, and a preferred range of those groups each is the same asthat of R¹. L⁸¹ and X⁸¹ have the same meanings as L¹ and X¹respectively, and preferred ranges thereof are the same as those of L¹and X¹ respectively. n⁸¹ represents an integer of 1 to 4, preferably 1or 2. n⁸² represents an integer of 0 to 3, preferably 0 or 1. n⁸³represents 1 or 2, preferably 2. n⁸⁴ represents 0 or 1.

Q⁸¹ represents atoms completing a nitrogen-containing aromatic ring. Q⁸¹may have a substituent on the ring (as examples of such a substituent,mention may be made of the groups recited in the explanations of R¹).Examples of a nitrogen-containing aromatic ring completed by Q⁸¹ includea pyridine ring, a pyrazine ring, a pyrimidine ring, a pyrazole ring, anoxazole ring, an imidazole ring, a triazole ring, an oxadiazole ring, abenzazole ring (such as a benzoxazole, benzimidazole or benzothiazolering), and a quinoline ring. Of these rings, a pyridine ring and abenzazole ring are preferred over the others. In particular, it isadvantageous that the ring completed by Q⁸¹ is a pyridine ring.

Q⁸² represents atoms completing an aromatic ring. Q⁸² may have asubstituent on the ring (as examples of such a substituent, mention maybe made of the groups recited in the explanations of R¹). Examples of anaromatic ring completed by Q⁸² include a benzene ring, a naphthalenering, an anthracene ring, a phenanthrene ring, a pyridine ring, apyrazine ring, a quinoline ring, a thiophene ring, and a furan ring. Ofthese rings, a benzene ring, a pyridine ring, a pyrazine ring and athiophene ring are preferred over the others. In particular, it isadvantageous that the ring completed by Q⁸² is a benzene ring.

The present compound may be a low molecular weight compound, or anoligomer or polymer compound containing repeating units represented byformula (1) in the main chain and/or side chains (suitable mass-averagemolecular weight (on a polystyrene basis) of which is in the range of1,000 to 5,000,000, preferably 2,000 to 1,000,000, particularlypreferably 3,000 to 100,000). It is advantageous that the presentcompound is a low molecular weight compound.

Examples of the present compound are illustrated below, but it should beunderstood that these examples are not to be construed as limiting thescope of the invention in any way.

The compounds according to the invention can be synthesized usingvarious methods. For instance, they each can be obtained by mixingphosphorus ligand(s) and various other ligands, or these ligands indissociated states, with a transition metal compound, wherein a solvent(such as a halogen-containing solvent, an alcoholic solvent, an ethersolvent or water) may be present or absent, a base (with examplesincluding various inorganic and organic bases, such as sodium methoxide,potassium t-butoxide, triethylamine and potassium carbonate) may bepresent or absent and the temperature may be kept below room temperatureor raised by heating in a usual way, by microwave heating, or the like.

Next, descriptions of light-emitting devices containing the presentcompounds are provided. To light-emitting devices according to theinvention, it does not much matter what system, operation method andutilization mode are adopted so long as the devices use the presentcompounds. However, the present devices prefer to utilize luminescencefrom the present compounds or to use the present compounds as electrontransport materials. As typical examples of a light-emitting device,mention maybe made of organic EL (electroluminescence) devices.

In the light-emitting device according to the invention, thelight-emitting layer preferably comprises the present compound, that isa guest compound, doped into a host compound (a guest compoundcorresponds to a compound having a transition metal atom-phosphorus atombond). T₁ level (the energy level of the lowest excited triplet state)of the host compound is preferably higher than that of the guestcompound. T₁ level of the host compound is preferably from 260 kJ/mol to356 kJ/mol (from 62 kcal/mol to 85 kcal/mol), more preferably, from 272kJ/mol to 335 kJ/mol (from 65 kcal/mol to 80 kcal/mol).

T₁ level of a compound, which is included in a layer being contact withthe light-emitting layer such as a hole transport layer, an electrontransporting layer, a hole blocking layer and the like, is preferablyhigher than that of the guest compound included in the light-emittinglayer. T₁ level of the compound included in a layer being contact withthe light-emitting layer is preferably from 260 kJ/mol to 356 kJ/mol(from 62 kcal/mol to 85 kcal/mol), more preferably, from 272 kJ/mol to335 kJ/mol (from 65 kcal/mol to 80 kcal/mol). As the compound whichmeets above described range of T₁ level, the compounds disclosed inJapanese Patent application No. 2001-197135 and 2001-76704 is suitablyused. The preferable range of the compound is also disclosed in JapanesePatent application No. 2001-197135 and 2001-76704.

The organic layers of the light-emitting devices containing the presentcompounds are not particularly limited in their formation methods, butthey can be formed using, e.g., a resistance heating vapor depositionmethod, an electron beam method, a sputtering method, a molecularlamination method, a coating method, an inkjet method, a printing methodor a transfer method. Of these methods, the resistance heating vapordeposition method and the coating method are preferred in thecharacteristic and manufacturing aspects.

Every light-emitting device according to the invention is a devicecomprising a pair of electrodes, namely an anode and a cathode, and alight-emitting layer or at least two thin layers (films) of organiccompounds, inclusive of a light-emitting layer, sandwiched between theelectrodes. The thin layers the device may have in addition to thelight-emitting layer are, e.g., a hole injection layer, a hole transportlayer, an electron injection layer, an electron transport layer and aprotective layer. Each of these layers may have another function. Forforming each of those layers, various materials can be employed.

The anode supplies holes to a hole injection layer, a hole transportlayer and a light-emitting layer. As anode materials, metals, alloys,metal oxides, electrically conductive materials and mixtures thereof,preferably materials having a work function of at least 4 eV, can beused. Examples of such materials include electrically conductive metaloxides, such as tin oxide, zinc oxide, indium oxide and indium tin oxide(ITO), metals such as gold, silver, chromium and nickel, mixtures orlaminates of those metals and electrically conductive metal oxides,electrically conductive inorganic materials such as copper iodide andcopper sulfide, electrically conductive organic materials such aspolyaniline, polythiophene and polypyrrole, and laminates of thoseelectrically conductive materials and ITO. Of the materials recitedabove, the electrically conductive metal oxides are preferred. Inparticular, ITO is advantageous over the others from the viewpoints ofproductivity, conductivity and transparency. The suitable thickness ofthe anode, though can be selected depending on the anode material, isgenerally from 10 nm to 5 μm, preferably 50 nm to 1 μm, particularlypreferably 100 nm to 500 nm.

In general the anode is used in the state of a layer formed on a sodalime glass, alkali-free glass or transparent resin substrate. In thecase of using a glass substrate, alkali-free glass is preferred from theviewpoint of reduction in ions eluted from the glass. When soda limeglass is used for the substrate, it is appropriate that a barrier coatof silica be provided on the glass substrate. The substrate thicknesshas no particular limitation so long as the substrate can ensuremechanical strength for the anode. For instance, the suitable thicknessof a glass substrate is at least 0.2 mm, preferably at least 0.7 mm.

The methods suitable for making the anode vary with the material used.In the case of ITO, for instance, the film formation can be carried outusing an electron beam method, a sputtering method, a resistance heatingvapor deposition method, a chemical reaction method (e.g., sol-gelmethod) or the method of coating a dispersion of indium tin oxide.

Washing and other treatments for the anode enable the device to get areduction in operation potential and elevation of light-emittingefficiency. In the case of an anode using ITO, it is effective for theanode to receive UV-ozone treatment or plasma treatment.

The cathode supplies electrons to an electron injection layer, anelectron transport layer and a light-emitting layer. In selecting thecathode, the adhesion to a layer adjacent to the cathode, such as anelectron injection layer, an electron transport layer or alight-emitting layer, the ionization potential and the stability aretaken into consideration. As cathode materials, metals, alloys, metalhalides, metal oxides, electrically conductive materials and mixturesthereof can be employed. Examples of such materials include alkalimetals (e.g., Li, Na, K) and the fluorides or oxides thereof, alkalineearth metals (e.g., Mg, Ca) and the fluorides or oxides thereof, gold,silver, lead, aluminum, Na—K alloy or mixture, Li—Al alloy or mixture,Mg—Ag alloy or mixture, and rare earth metals such as indium andytterbium. Of these materials, the materials having a work function ofat most 4 eV are preferred over the others. In particular, aluminum,Li—Al alloy or mixture and Mg—Ag alloy or mixture are used to advantage.The cathode may have a single-layer structure formed of the compound ormixture as recited above or a lamination structure comprising thecompounds or/and mixtures as recited above. For instance, an Al/LiFlamination structure and an Al/Li₂O lamination structure are appropriatefor the cathode. The suitable thickness of the cathode, though can bechosen depending on the cathode material, is generally from 10 nm to 5μm, preferably 50 nm to 1 μm, particularly preferably 100 nm to 1 μm.

In making the cathode, various known methods, such as an electron beammethod, a sputtering method, a resistance heating vapor depositionmethod and a coating method, can be adopted. The metals as recited abovemay be evaporated independently, or two or more thereof may beevaporated simultaneously. Further, it is possible to evaporate aplurality of metals at the same time to form an alloy electrode, or thepreviously prepared alloy may be subjected to vapor deposition.

It is appropriate for the light-emitting device that both anode andcathode have low sheet resistance, specifically several hundredsΩ/square at the highest.

For a light-emitting layer, any materials can be used so long as theycan form a layer having the following functions. One function is toreceive hole injection from the anode, the hole injection layer or thehole transport layer as well as electron injection from the cathode, theelectron injection layer or the electron transport layer when theelectric field is applied to the light-emitting device. Another functionis to permit the charges injected in the layer to move. The otherfunction is to enable the emission of light by providing a place forrecombining holes and electrons. Further, it does not matter tomaterials used for the light-emitting layer whether luminescence isproduced from singlet-state excitons or triplet-state excitons so longas they can produce luminescence. Examples of such materials includebenzoxazole derivatives, benzimidazole derivatives, benzothiazolederivatives, styrylbenzene derivatives, polyphenyl derivatives,diphenylbutadiene derivatives, tetraphenylbutadiene derivatives,naphthalimide derivatives, coumarin derivatives, perylene derivatives,perinone derivatives, oxadiazole derivatives, aldazine derivatives,pyraridine derivatives, cyclopentadiene derivatives, bisstyrylanthracenederivatives, quinacridone derivatives, pyrrolopyridine derivatives,thiadiazolopyridine derivatives, styrylamine derivatives, aromaticdimethylidyne derivatives, various metal complexes represented by metalor rare earth complexes of 8-quinolinol derivatives, polymeric compoundssuch as polythiophene, polyphenylene and polyphenylenevinylene,organosilane derivatives, and the present compounds. Although thelight-emitting layer has no particular restrictions as to the thickness,the suitable thickness thereof is generally from 1 nm to 5 μm,preferably 5 nm to 1 μm, particularly preferably 10 nm to 500 nm.

The suitable proportion of the present compound in the light-emittinglayer is from 0.1 to 100%, preferably from 1 to 50%, particularlypreferably from 5 to 30%, to the total mass of the light-emitting layer.

The light-emitting layer may be formed of a single compound or apluratity of compounds. And the light-emitting layer may be constitutedof one layer or two or more layers. In the latter case, thelight-emitting layer may be designed so that the constituent layersthereof radiate differently colored beams respectively, therebyproducing, e.g., white luminescence. In the former case also, thelight-emitting layer may produce white luminescence. Further, each ofthe layers constituting the light-emitting layer may be formed of asingle material or more than one compound.

As to the method of forming the light-emitting layer, there is noparticular restriction, but various methods can be adopted. Forinstance, a resistance heating vapor deposition method, an electron beammethod, a sputtering method, a molecular lamination method, a coatingmethod (e.g., a spin coating, cast coating or dip coating method), anink jet method, a printing method, an LB method and a transfer methodare usable herein. Of these methods, a resistance heating vapordeposition method and a coating method are preferred over the others.

The materials for a hole injection layer and a hole transport layer maybe any materials so long as they have any one of the functions as aninjector of holes from the anode, a transporter of holes and a barrieragainst electrons injected from the cathode. Examples of materialshitherto known to have one of such functions include carbazolederivatives, triazole derivatives, oxazole derivatives, oxadiazolederivatives, imidazole derivatives, polyarylalkane derivatives,pyrazoline derivatives, pyrazolone derivatives, phenylenediaminederivatives, arylamine derivatives, amino-substituted chalconederivatives, styrylanthracene derivatives, fluorenone derivatives,hydrazone derivatives, stilbene derivatives, silazane derivatives,aromatic tertiary amine compounds, styrylamine compounds, aromaticdimethylidyne compounds, porphyrin compounds, polysilane compounds,electrically conductive polymers and oligomers such aspoly(N-vinylcarbazole) derivatives, aniline copolymers, thiopheneoligomers and polythiophene, organic silane compounds, carbon film, andthe present compounds. The suitable thickness of the hole injectionlayer and the hole transport layer each, though it has no particularlimitation, is generally from 1 nm to 5 μm, preferably 5 nm to 1 μm,particularly preferably 10 nm to 500 nm. Each of the hole injectionlayer and the hole transport layer may have a single-layer structureconstituted of one or more of the materials recited above or amultiple-layer structure made up of at least two layers having the samecomposition or different compositions.

As a method for forming the hole injection layer and the hole transportlayer, a vacuum evaporation method, an LB method, a method of coatingsolutions or dispersions of hole-injecting and transporting agents (bythe use of, e.g., a spin coating, cast coating or dip coating method),an ink jet method, a printing method or a transfer method can beadopted. When the coating method is adopted, the agents to constitutethose layers may be dissolved or dispersed in a coating solvent,together with a resinous ingredient. Examples of such a resinousingredient include polyvinyl chloride, polycarbonate, polystyrene,polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone,polyphenylene oxide, polybutadiene, poly(N-vinylcarbazole), hydrocarbonresin, ketone resin, phenoxy resin, polyamide, ethyl cellulose,polyvinyl acetate, ABS resin, polyurethane, melamine resin, unsaturatedpolyester resin, alkyd resin, epoxy resin and silicone resin.

The materials for the electron injection layer and the electrontransport layer may be any materials so long as they have any one of thefunctions as an injector of the electrons from the cathode, atransporter of electrons and a barrier against holes injected from theanode. Examples of materials known to have such functions includetriazole derivatives, oxazole derivatives, oxadiazole derivatives,imidazole derivatives, fluorenone derivatives, anthraquinodimethanederivatives, anthrone derivatives, diphenylquinone derivatives,thiopyran dioxide derivatives, carbodimide derivatives,fluorenylidenemethane derivatives, distyrylpyrazine derivatives,tetracarboxylic acid anhydrides of aromatic condensed rings such asnaphthalene and perylene, phthalocyanine derivatives, various metalcomplexes represented by metal complexes of 8-quinolinol derivatives,metallophthalocyanines and metal complexes having benzoxazole orbenzothiazole ligands, organosilane derivatives and the presentcompounds. The suitable thickness of the electron injection layer andthe electron transport layer each, though it has no particularlimitation, is generally from 1 nm to 5 μm, preferably 5 nm to 1 μm,particularly preferably 10 nm to 500 nm. Each of the electron injectionlayer and the electron transport layer may have a single-layer structureconstituted of one or more of the materials as recited above, or amultiple-layer structure made up of at least two layers having the samecomposition or different compositions.

As a method of forming the electron injection layer and the electrontransport layer, a vacuum evaporation method, an LB method, a method ofcoating solutions or dispersions of electron-injecting and transportingagents as recited above (by the use of, e.g., a spin coating, castcoating or dip coating method), an ink jet method, a printing method ora transfer method can be adopted. In the case of adopting a coatingmethod, the electron-injecting and transporting agents can be dissolvedor dispersed together with a resinous ingredient. Examples of a resinousingredient usable therein include the same resins as employed for thehole injection and transport layers.

The materials for a protective layer may be any substances so long asthey have a function capable of inhibiting the invasion of a devicedeterioration promoter, such as moisture or oxygen, into the device.Examples of such a substance include metals such as In, Sn, Pb, Au, Cu,Ag, Al, Ti and Ni, metal oxides such as MgO, SiO, SiO₂, Al₂O₃, GeO, NiO,CaO, BaO, Fe₂O₃, Y₂O₃ and TiO₂, metal nitrides such as SiN_(x) andSiN_(x)O_(y), metal fluorides such as MgF₂, LiF, AlF₃ and CaF₂,polyethylene, polypropylene, polymethyl methacrylate, polyimide,polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene,polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene anddichlorodifluoro-ethylene, a copolymer prepared by polymerizing amixture of tetrafluoroethylene and at least one comonomer,fluorine-containing copolymers having cyclic structures on the mainchain, a water-absorbing substance having a water absorption rate of atleast 1%, and a moisture-proof substance having a water absorption rateof at most 0.1%.

The protective layer also has no particular restriction as to theformation method, but any of a vacuum evaporation method, a sputteringmethod, a reactive sputtering method, a molecular beam epitaxy (MBE)method, a cluster ion beam method, an ion plating method, a plasmapolymerization method (high frequency excitation ion plating method), aplasma chemical vapor deposition (CVD) method, a laser CVD method, aheat CVD method, a gas source CVD method, a coating method, a printingmethod and a transfer method can be adopted for the formation thereof.

EXAMPLE

The present invention will now be illustrated in more detail byreference to the following examples. However, embodiments of theinvention should not be construed as being limited to these examples.

Synthesis of Compound (1-1):

Chloroform in an amount of 20 ml was added to 0.2 g of an iridiumcomplex “a” (prepared referring to the method described in J. Am. Chem.Soc., 1984, 106, 6647) and 0.17 g of triphenyl phosphine, and stirredunder reflux for 3 hours. After cooling to room temperature, thereaction solution was purified by column chromatography on silica gel(developing solvent: chloroform) to yield 0.1 g of a pale yellow solid(1-1). After it was de-aerated, the solid (1-1) (solvent: toluene,concentration: 5.0×10⁻⁶ M) was examined for luminescence, and theluminescence produced thereby was found to have λmax at 470 nm. Althoughthe iridium complex “a” was examined for luminescence under the samecondition as the solid (1-1), no luminescence was observed.

Synthesis of Compound (1-13):

Chloroform in an amount of 20 ml was added to 0.2 g of an iridiumcomplex “a” and 0.12 ml of triethyl phosphite, and stirred under refluxfor 3 hours. After cooling to room temperature, the reaction solutionwas purified by column chromatography on silica gel (developing solvent:chloroform) to yield 0.13 g of a pale yellow solid (1-13). After it wasde-aerated, the solid (1-13) (solvent: toluene, concentration: 5.0×10⁻⁶M) was examined for luminescence, and the luminescence produced therebywas found to have λmax at 465 nm.

Synthesis of Compound (1-61):

Chloroform in an amount of 20 ml was added to 1.0 g of an iridiumcomplex “b” (prepared referring to the method described in J. Am. Chem.Soc., 1984, 106, 6647) and 1.2 g of a phosphine ligand “c”, and stirredunder reflux for 3 hours. After cooling to room temperature, thereaction solution was purified by column chromatography on silica gel(wherein the chromatogram was developed using chloroform first and thena chloroform-methanol mixture) to yield 0.8 g of a pale yellow solid. Tothis solid were added sequentially 30 ml of methanol and 0.5 g ofNaClO₄.H₂O. The thus deposited solid was filtered off, and then washedwith methanol. The resulting solid was recrystallized from achloroform-hexane mixture to yield 0.5 g of a white solid (1-61). Thestructure of the white solid was confirmed by NMR. After it wasde-aerated, the solid (1-61) (solvent: toluene, concentration: 5.0×10⁻⁶M) was examined for phosphorescence, and the phosphorescence producedthereby was found to have λmax at 440 nm. The quantum yield φ of thisphosphorescence was 60%.

Synthesis of Compound (1-70):

Chloroform in an amount of 10 ml was added to 0.2 g of an iridiumcomplex “b” and 0.17 g of a phosphine ligand “d”. To this solution, 0.1ml of a methanol solution of sodium methoxide (28 mass %) was furtheradded. The resulting admixture was stirred under reflux for 3 hours.After cooling to room temperature, the reaction solution was purified bycolumn chromatography on silica gel (wherein the chromatogram wasdeveloped using chloroform first and then a chloroform-methanol mixture)to yield 0.1 g of a yellow solid (1-70). The structure of the yellowsolid (1-70) was confirmed by measurement with a mass spectrometer.

Comparative Example 1

Poly(N-vinylcarbazole) in an amount of 40 mg, 12 mg of PBD[2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole] and 1 mg ofCompound (A) were dissolved in 2.5 ml of dichloroethane, and spin-coatedon a cleaned substrate (at 1,500 r.p.m. for 20 seconds). The thicknessof the thus formed organic layer was 98 nm. A patterned mask (foradjusting each emission area to 4 mm×5 mm) was put on the thin organiclayer, and installed in a vacuum evaporation apparatus. By the use ofthis apparatus, Mg and Ag were deposited simultaneously on the thinorganic layer via the patterned mask in a Mg/Ag ratio of 10/1, therebyforming a metallic film having a thickness of 50 nm. On this metallicfilm, Ag was further deposited into a 50 nm-thick film. The thusproduced EL device was made to luminesce by applying thereto a DCconstant voltage by means of a source measure unit, Model 2400, made byToyo Technica Co., Ltd., and examined for luminance and wavelengths ofluminescence by using a luminometer BM-8 made by Topcon Co. and aspectrum analyzer PMA-11 made by Hamamatsu Photonics Co. respectively.The luminescence thus produced had a green color, an ELmax value of 505nm and a CIE chromaticity (x, y) value of (0.27, 0.57).

Comparative Example 2

A device was produced and evaluated in the same manner as in ComparativeExample 1, except that Compound (B) was used in place of Compound (A).As a result, no luminescence was produced from the device.

Example 1

A device was produced in the same manner as in Comparative Example 1,except that the present Compound (1-13) was used in place of Compound(A). As a result, blue luminescence having an ELmax value of 475 nm wasobtained.

Example 2

On a cleaned substrate, Baytron P [a PEDOT-PSS solution(polydioxyethylenethienylene-polystyrenesulfonic acid doped material), aproduct of Bayer A. G.] was spin-coated (at 1,000 r.p.m. for 30 seconds)and dried at 150° C. under vacuum for 1.5 hours. The thus formed organiclayer had a thickness of 70 nm. On this layer was spin-coated (at 1,000r.p.m. for 20 seconds) a solution containing 10 mg ofpolymethylmethacrylate, 20 mg of Compound C and 1 mg of the presentCompound (1-61) in 2 ml of dichloroethane. The resulting substrate wasinstalled in a vacuum evaporation apparatus, and thereon a 36 nm-thickfilm of Compound D was formed by evaporation. On the thus formed organicthin layer, a patterned mask (for adjusting each emission area to 4 mm×5mm) was put, and thereon were formed a 3 nm-thick lithium fluoride filmfirst and then a 400 nm-thick aluminum film by evaporation. The thusproduced EL device was made to luminesce by applying thereto a DCconstant voltage by means of a source measure unit, Model 2400, made byToyo Technica Co., Ltd., and examined for luminance and wavelengths ofluminescence by using a luminometer BM-8 made by Topcon Co. and aspectrum analyzer PMA-11 made by Hamamatsu Photonics Co. respectively.The luminescence thus produced had a blue color, an ELmax value of 447nm and a CIE chromaticity (x, y) value of (0.19, 0.19) The externalquantum efficiency of the device was 0.5%.

Example 3

A device was produced and evaluated in the same manner as in Example 2,except that 10 mg of Compound C, 5 mg of the present Compound (1-61) and6 mg of Compound D were used in place of 20 mg of Compound C and 1 mg ofthe present Compound (1-61). As a result, blue luminescence having anELmax of 447 nm and a CIE chromaticity (x, y) value of (0.19, 0.24) wasobtained. The external quantum efficiency of this device was 1.3%.

Example 4

A cleaned ITO substrate was installed in a vacuum evaporation apparatus,and onto this substrate TPD (N,N′-diphenyl-N,N′-di(m-tolyl)benzidine)was evaporated into a 50 nm-thick film. Onto this film, Compound C andthe present Compound (1-70) were evaporated simultaneously in a ratio of17 to 1 (by mass), thereby forming a film having a thickness of 32 nm.Further thereon, a 36 nm-thick film of the azole Compound D was formedby vacuum evaporation, and subsequently thereto the same cathode as inExample 2 was formed by vacuum evaporation. The thus produced EL deviceprovided blue luminescence having a CIE chromaticity value of (0.18,0.36), and the external quantum efficiency thereof was 5.1%.

Similarly to the above, EL devices comprising other compounds accordingto the invention were produced and evaluated. As a result, it wasconfirmed that these devices were successful in producing blueluminescence although it had been difficult for hitherto known heavymetal complexes to enable the production of blue light-emitting devices.Further, it becomes possible to produce white light-emitting devices byapplications of the present compounds. Furthermore, high-efficiency bluelight-emitting devices which contain non-conjugate polymers (e.g.,polyvinylcarbazole) and conjugate polymers (e.g., polyolefin compounds)and are formed using a coating technique can be produced by utilizingthe present compounds.

The present blue light-emitting devices can be suitably used in variousareas, such as those of indicators, displays, backlight,electrophotography, light sources for illumination, recording, exposureand reading uses, beacons, signboards and interiors. In addition, thepresent compounds are applicable to medical-care uses, brighteningagents, photographic materials, UV absorbents, laser dyes, dyes forcolor filters, color conversion filters, and optical communications.

1. A light emitting device comprising: a pair of electrodes; and organiccompound layers comprising a light-emitting layer provided in betweenthe electrodes, wherein at least one of the organic compound layerscomprises a compound having a transition metal-phosphorus atom bond, andwherein the compound having a transition metal-phosphorus atom bond isrepresented by formula (1):

wherein M¹ represents rhodium (III), tungsten (O), or rhenium (I), R¹represents a hydrogen atom or a substituent, L¹ represents a ligand, X¹represents a counter ion, n¹ represents 2 or 3, n² represents an integerof 1 to 8, n³ represents an integer of 0 to 8, n⁴ represents an integerof 0 to 6, when at least one of n¹, n², n³ and n⁴ is more than one, R¹groups, (R¹)_(n1)—P ligand, L¹ ligands or X¹ ions are each the same ordifferent.
 2. The light-emitting device according to claim 1, wherein atleast one of R¹ represents a heteroaryl group.
 3. The light-emittingdevice according to claim 1, wherein at least one of R¹ represents aheteroaryloxy group.
 4. The light-emitting device according to claim 1,wherein at least one of R¹ represents a substituted amino group.
 5. Thelight-emitting device according to claim 1, wherein a plurality of R¹combine with each other to form a cyclic structure.
 6. Thelight-emitting device according to claim 1, wherein a plurality of R¹combine with each other to form a phosphinine ring.
 7. Thelight-emitting device according to claim 1, wherein at least one of R¹represents an alkoxy group.
 8. The light-emitting device according toclaim 1, wherein at least one of R¹ represents an aryloxy group.